Evaluating fault stability near tunnels: a numerical parametric study and a dimensionless safety approach

Ensuring the stability of faults near a tunnel is crucial for safety during excavation. This study presents a comprehensive numerical parametric analysis to evaluate fault stability in the context of tunnel construction. The analysis examines several key parameters, including fault mechanical properties, tunnel depth, fault angle, tunnel size, the distance between the fault and tunnel, and the initial stress state of the surrounding rock. These factors significantly affect stress distribution and potential fault movement, which are critical for maintaining tunnel stability. The findings emphasize the importance of specific factors, such as fault angle, the ratio of tunnel size to fault distance, and the initial stress state, in determining fault stability. To account for the interaction between these variables, a dimensionless parameter is developed, incorporating all these factors into a simplified metric for assessing the factor of safety in fault stability. A strong correlation between this dimensionless parameter and the factor of safety is established, offering a reliable method with minimal error. Finally, a case study is presented to verify the proposed safety approach, demonstrating its ability to accurately predict both the factor of safety and the location of fault slipping.